21121212100 has 18 divisors (see below), whose sum is σ = 45833030474. Its totient is φ = 8448484800.

The previous prime is 21121212089. The next prime is 21121212103. The reversal of 21121212100 is 121212112.

It can be written as a sum of positive squares in 3 ways, for example, as 5053504 + 21116158596 = 2248^2 + 145314^2 .

It is a super-2 number, since 2×21121212100² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21121212103) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 105605961 + ... + 105606160.

Almost surely, 2^21121212100 is an apocalyptic number.

21121212100 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21121212100 is an abundant number, since it is smaller than the sum of its proper divisors (24711818374).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21121212100 is a wasteful number, since it uses less digits than its factorization.

21121212100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 211212135 (or 211212128 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 13.

Adding to 21121212100 its reverse (121212112), we get a palindrome (21242424212).

It can be divided in two parts, 21 and 121212100, that added together give a palindrome (121212121).

The spelling of 21121212100 in words is "twenty-one billion, one hundred twenty-one million, two hundred twelve thousand, one hundred".